1. Field of the Invention
The present invention relates to a push button switch assembly which is suitable for use in operation panels of electronic equipments, input devices of OA (office automation) apparatus, etc.
2. Statement of the Related Art
A conventional push button switch assembly will first be described below with reference to FIGS. 9 and 10. FIG. 9 is a top view of a keyboard in part used for the push button switch assembly. FIG. 10 is a side sectional view of the push button switch assembly corresponding to a portion A shown in FIG. 9.
Referring now to FIG. 10, a reference numeral 5 denotes a casing in which a button 4 is vertically movably mounted. A push button switch assembly which will be described hereinbelow is provided below this button 4. A reference numeral la denotes a flexible connector which is coupled to a substrate 1 as hereinbelow described and which is adapted for transmitting the state of switching of the push button switch assembly to a main body of an equipment involved.
Next, the conventional push button switch assembly which corresponds to a subject matter of the present invention will be described. The substrate 1 has a pair of stationary contacts 1a and 1b. On this substrate 1 there is disposed a cup-shaped rubber contact 2. The casing 5, which has the button 4 mounted in its cylindrical slide hole 3, is configured such that the rubber contact 2 and the slide hole 3 are in alignment with each other. The button 4 has an indicating section 4a on its upper surface. The button 4 further has claw portions 6 engageable with apertures in the casing 5 as well as a slide portion 7 slidable on the inner wall surface of the slide hole 3. A cylindrical slider body 8, which is slidable on the inner wall surface of the slide portion 7, is mounted inside of the same 7. Within this slider body 8 there is mounted a coil spring 9 for causing the slider body 8 to be pressed against the rubber contact 2.
In the above-described prior art push button switch assembly, when assembled, the casing 5 is first engaged with the button 4 and then the coil spring 9 and the slider body 8 are sequentially inserted into the button 4 and finally the substrate having the rubber contact 2 and the stationary contacts 1a, 1b is mounted on the casing 5.
The operation of the above-described prior art push button assembly will now be described. As the button 4 is depressed, the coil spring 9 is compressed. This compressing force is transmitted to the rubber contact 2 through the slider body 8 until the conduction between the contacts 1a and 1b becomes effective by means of the rubber contact 2. When the button 4 is further depressed, the button 4 is moved until a flat surface portion 10 of the back surface thereof abuts against the top surface portion 11 of the cylindical slide hole 3, thus being moved by a distance corresponding to a full stroke. During this movement, the slider body 8, which acts to apply the force to the rubber contact 2, performs its vertical parallel movement. In this way, in the prior art technique wherein the slider body 8 is provided inside of the button 4, a more stable pressing force is applied to the rubber contact 2 as compared with a case where the rubber contact 2 is directly pressed by the coil spring 9.